The guide vanes and rotor blades of gas turbines are exposed to strong loads. To keep the leakage losses from the gas turbine at low levels, by way of example the rotor of the gas turbine is fitted with a very small amount of play with respect to the stator, so that a stripping action occurs. A honeycomb structure is provided at the stator of the gas turbine. The honeycomb structure comprises a metal alloy which is able to withstand high temperatures. A further design involves the use of smooth, coated or uncoated heat shield segments (HSS) which are positioned radially opposite the rotating blade at the outer radius. The blade tip then rubs against these heat shield segments. To prevent the blade tip itself from being abraded, the tip may be coated in order then to abrade the heat shield segments to a greater extent. However, one drawback of this embodiment is that the coating has only a limited adhesion to the turbine blade. A further drawback is that cooling-air bores, with which either the heat shield segment and/or the blade may be provided, become blocked during the frictional action.
It is known from documents DE-C2 32 35 230, EP 132 667 or DE-C2 32 03 869 to use metal felts at various locations of gas turbine components, for example at the tip of a turbine blade or vane (DE-C2 32 03 869), between a metal core or a ceramic outer skin (DE-C2 32 35 230) or as a cladding of the turbine blade or vane (EP-B1 132 667). However, these embodiments have the drawback that the metal felt which is used is insufficiently resistant to oxidation. The increases in the hot-gas temperatures, for example in modern gas turbines, lead to the materials used having to satisfy ever greater demands. However, the metal felts in the abovementioned documents no longer satisfy the requirement to current levels, in particular with regard to the required resistance to oxidation. U.S. Pat. No. 6,241,469 B1, U.S. Pat. No. 6,312,218 B1, DE-A1 199 12 701, EP-A2 0 916 897 and EP-A2 1 076 157 have disclosed metal felts which are composed of an intermetallic alloy. These felts consist of sintered and pressed intermetallic fibers, and on account of the intermetallic phases have significantly improved materials properties than the abovementioned materials in terms of strength, resistance to oxidation, deformability and abradability. Metallic high-temperature fibers have also been described in VDI Report 1151, 1995 (Metallische Hochtemperaturfasern durch Schmelzextraktion—Herstellung, Eigenschaften, Anwendungen) [Metallic high-temperature fibers through melt extraction—production, properties, uses].